Track DMX packet senders and expose via API

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

senders/senders.go

@@ -0,0 +1,67 @@
+package senders
+
+import (
+	"net"
+	"sync"
+	"time"
+
+	"github.com/gopatchy/artmap/config"
+)
+
+type SenderInfo struct {
+	Universe config.Universe `json:"universe"`
+	IP       string          `json:"ip"`
+}
+
+type senderKey struct {
+	protocol config.Protocol
+	universe uint16
+	ip       string
+}
+
+type UniverseSenders struct {
+	mu      sync.Mutex
+	entries map[senderKey]time.Time
+}
+
+func New() *UniverseSenders {
+	return &UniverseSenders{
+		entries: map[senderKey]time.Time{},
+	}
+}
+
+func (s *UniverseSenders) Record(u config.Universe, ip net.IP) {
+	key := senderKey{
+		protocol: u.Protocol,
+		universe: u.Number,
+		ip:       ip.String(),
+	}
+	s.mu.Lock()
+	s.entries[key] = time.Now()
+	s.mu.Unlock()
+}
+
+func (s *UniverseSenders) Expire(maxAge time.Duration) {
+	cutoff := time.Now().Add(-maxAge)
+	s.mu.Lock()
+	for k, t := range s.entries {
+		if t.Before(cutoff) {
+			delete(s.entries, k)
+		}
+	}
+	s.mu.Unlock()
+}
+
+func (s *UniverseSenders) GetAll() []SenderInfo {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	result := make([]SenderInfo, 0, len(s.entries))
+	for k := range s.entries {
+		result = append(result, SenderInfo{
+			Universe: config.Universe{Protocol: k.protocol, Number: k.universe},
+			IP:       k.ip,
+		})
+	}
+	return result
+}